#include <stdio.h>

int main()
{
    int a,n;
    double x,b[99999],sum;
    scanf("%lf",&x);
    for(a=1;;a++)
        {
            n=a;
            b[1]=2;
            b[n+1]=b[a]*0.980;
            sum=sum+b[a];
            if(sum>=x)
                break;
        }
    printf("%d",a);
    return 0;
}